Trump seems to be courting the Dem vote. We have to remember that Trump was a Dem for most of his life and only became a GOPer for reasons of political expediency.
Trump is trying to win the nomination by any means necessary, even if it is rude, crude, or even morally wrong.
He fights like a Democrat.
It works, unfortunately, which is why they do it and why he does it, and why campaigns have always been grisly, skin crawling affairs from the beginning.
Then after they get the nomination they expect the party, including those they defeated, to get over it and put aside personal feelings and support them for the sake of the greater good. In other words, they are brutal but it isn’t personal to them, it’s just business, just politics.